U.S. patent application number 13/809028 was filed with the patent office on 2013-05-02 for sliding member.
This patent application is currently assigned to DAIDO METAL COMPANY LTD.. The applicant listed for this patent is Shigeru Inami, Yukihiko Kagohara, Koji Zushi. Invention is credited to Shigeru Inami, Yukihiko Kagohara, Koji Zushi.
Application Number | 20130108198 13/809028 |
Document ID | / |
Family ID | 45441303 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130108198 |
Kind Code |
A1 |
Zushi; Koji ; et
al. |
May 2, 2013 |
SLIDING MEMBER
Abstract
Slide member is provided with an Cu-based bearing alloy layer
including hard particles, and DLC layer laminated over Cu-based
bearing alloy layer. At least some of the hard particles included
in Cu-based bearing alloy layer are exposed on DLC layer side
surface.
Inventors: |
Zushi; Koji; (Inuyama-shi,
JP) ; Inami; Shigeru; (Inuyama-shi, JP) ;
Kagohara; Yukihiko; (Inuyama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zushi; Koji
Inami; Shigeru
Kagohara; Yukihiko |
Inuyama-shi
Inuyama-shi
Inuyama-shi |
|
JP
JP
JP |
|
|
Assignee: |
DAIDO METAL COMPANY LTD.
Nagoya-shi, Aichi
JP
|
Family ID: |
45441303 |
Appl. No.: |
13/809028 |
Filed: |
July 7, 2011 |
PCT Filed: |
July 7, 2011 |
PCT NO: |
PCT/JP2011/065592 |
371 Date: |
January 8, 2013 |
Current U.S.
Class: |
384/276 |
Current CPC
Class: |
F16C 33/124 20130101;
Y10T 428/265 20150115; F16C 2206/40 20130101; Y10T 428/252
20150115; C23C 28/046 20130101; C23C 28/04 20130101; F16C 33/043
20130101; F16C 33/127 20130101; Y10T 428/24983 20150115; F16C
2204/10 20130101; C23C 16/26 20130101; Y10T 428/30 20150115; C23C
14/0605 20130101; Y10T 428/31678 20150401; F16C 2206/04
20130101 |
Class at
Publication: |
384/276 |
International
Class: |
F16C 33/04 20060101
F16C033/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2010 |
JP |
2010-156683 |
Claims
1. A slide member comprising: a Cu-based bearing alloy layer
including hard particles; and a DLC layer laminated over the
Cu-based bearing alloy layer; wherein at least some of the hard
particles included in the Cu-based bearing alloy layer are exposed
on a DLC layer side surface.
2. The slide member according to claim 1, wherein the hard
particles comprise at least one type of compound selected from a
group consisting of boride, silicide, oxide, nitride, carbide, and
intermetallic compound, and wherein the particle diameter of the
hard particles averages from 0.5 to 20 (.mu.m).
3. The slide member according to claim 2, wherein the hard
particles comprise a metal silicide or a metal carbide.
4. The slide member according to according to claim 1, wherein the
hard particles exposed on the DLC side surface are spaced from one
another by an average distance ranging from 3 to 50 (.mu.m).
5. The slide member according to claim 1, wherein the hard
particles exposed on the DLC side surface occupy an area percentage
ranging from 0.1 (%) to 14 (%).
6. The slide member according to claim 1, wherein
A.gtoreq.0.5.times.T, where A (%) represents an area percentage of
the hard particles exposed on the DLC layer side surface and T
(.mu.m) represents a thickness of the DLC layer.
7. The slide member according to claim 1, wherein H.ltoreq.10000/T,
where H (HV) represents a hardness of the DLC layer and T (.mu.m)
represents a thickness of the DLC layer.
8. The slide member according to claim 7, wherein the DLC layer
satisfies H.ltoreq.6000, and T.ltoreq.15.
9. The slide member according to claim 1, wherein a hardness of the
DLC layer is 1.1 times or greater a hardness of the Cu-based
bearing alloy layer and 0.9 times or less a hardness of a counter
element with which the DLC layer slides.
Description
TECHNICAL FIELD
[0001] The present invention relates to a slide member provided
with a diamond-like carbon layer over a bearing alloy layer.
BACKGROUND
[0002] A slide member such as a slide bearing provided with a
bearing alloy layer comprising Al alloy or Cu alloy exhibits
relatively good initial conformability and outstanding fatigue
resistance and wear resistance. Such slide member is employed in
bearings for high output engines used, for instance, in automobile
and industrial machines in general. A slide member with further
improved bearing properties is desired with improvement in engine
performance.
[0003] A slide member with improved bearing properties, namely
conformability and wear resistance is disclosed in JP 2001-165167
A. The disclosed slide member has a bearing alloy layer comprising
Al alloy or Cu alloy which has annular protrusions formed on it.
The slide member further has a diamond-like carbon layer on the
surface of the annular protrusions. The document teaches that the
conformability of the disclosed, slide member is improved because
the annular protrusions are plastic deformation prone when
subjected to the load, applied, by the counter element. The
document further teaches that the disclosed slide member exhibits
good wear resistance because of the diamond like carbon layer
provided, on the surface of the bearing alloy layer.
[0004] In addition to improvement in conformability and wear
resistance, reduced friction coefficient is emerging as a further
desired improvement in bearing properties.
SUMMARY OF THE INVENTION
Problems to be Overcome
[0005] The present invention is based on the above described
background and one object of the present invention is to provide a
slide member with reduced fiction coefficient.
MEANS TO OVERCOME THE PROBLEM
[0006] In one embodiment of the present invention, a slide member
includes a Cu-based bearing alloy layer including hard particles;
and a DLC layer laminated over the Cu-based bearing alloy layer;
wherein at least some of the hard particles included in the
Cu-based bearing alloy layer are exposed on a DLC layer side
surface.
[0007] The Cu-based bearing alloy layer is Cu based, and includes
hard, particles and other components as required. Some of the hard
particles within the Cu-based bearing alloy layer are exposed, on
the DLC (Diamond-Like Carbon) surface side. It is to be appreciated
that the hard particles exposed to the surface in the DLC layer
side indicate hard particles that are not covered by the Cu matrix.
Thus, the hard particles exposed on the DLC layer side surface
include hard particles that protrude toward the DLC layer side from
the DLC layer side surface of the Cu-based bearing alloy layer. The
hard particles exposed on the DLC layer side can be obtained
through adjustments in the percentage (weight%) of the hard
particles contained in the Cu-based bearing alloy layer and the
particle diameter of the hard particles.
[0008] The Cu-based bearing alloy layer may be provided over a
metal backing made, for instance, of iron. Further, a bonding layer
may be provided between the metal backing and the Cu-based bearing
alloy layer to improve the bondability of the metal backing and the
Cu-based bearing alloy layer. The bonding layer, in this case,
preferably comprises a Cu plating layer.
[0009] In the present embodiment, the hard particles comprises at
least one type of compound selected from a group consisting of
boride, silicide, oxide, nitride, carbide, and intermetallic
compound, and the particle diameter of the hard particle averages
from 0.5 to 20 (.mu.m) .
[0010] A boride preferably comprises NiB, Ni.sub.3B, CrB,
ZrB.sub.2, CoB, TiB.sub.2, VB.sub.2, TaB.sub.2, WB, MoB, Fe--B
system or the like. A silicide preferably comprises TiSi.sub.2,
WSi.sub.2, MoSi.sub.2, TaSi.sub.2, CrSi.sub.2, Fe--Si system,
Mn--Si system, or the like. An oxide preferably comprises
SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, WO, MoO.sub.3,
Mn--O system, Fe--O system, V--O system, or the like. A nitride
preferably comprises, Si.sub.2N.sub.4, TiN, ZrN, TaN, VN, AIN,
C--BN, Cr.sub.2N, or the like. A carbide preferably comprises WC,
W.sub.2C, SiC, B.sub.4C, TiC, TaC, VC, ZrC, Mo.sub.2C or the like.
An intermetallic compound preferably comprises Ni--Sn system, Fe--W
system, Fe--Mo system, Fe--Mn system, Fe--Cr system, Fe--Al system,
Cr--Al system, V--Al system, Ti--Al system, W--Al system, or the
like.
[0011] Hard particles may further comprise other types of materials
such as Ni-based autogenous alloy (Ni--B--Si system), Co-based
autogenous alloy (Co--Mo--Si--B system), C, W or Mo.
[0012] Further, the hard particles comprising metal silicide and
metal carbide is particularly preferable.
[0013] Arranging the average particle diameter of the hard
particles to 0.5 (.mu.m) or greater facilitates exposure of the
hard particles on the DLC layer side surface of the Cu-based
bearing alloy layer. Arranging the average particle diameter of the
hard particles to 20 (.mu.m) or less facilitates dispersion of the
hard particles within the Cu-based bearing alloy layer. Thus, the
average particle diameter of the hard particles is configured to
range from 0.5 to 20 (.mu.m). Thus, relatively greater amount of
the hard particles are allowed to be exposed on the DLC layer side
surface of the Cu-based bearing alloy layer even when the
percentage in the amount of the hard particles within the Cu-based
bearing alloy layer is relatively less. The average particle
diameter preferably ranges between 1 to 10 (.mu.m). In the present,
embodiment, the average particle diameter of the hard particles is
measured, for instance, by fischer method.
[0014] Ready-made hard particles available in the market may be
employed in which the particle diameter is pre-arranged.
[0015] The primary component of the DLC layer is an amorphous
material comprising hydrogen carbide or an allotrope of carbon. The
DLC layer is formed over the Cu-based bearing alloy layer by plasma
enhanced chemical vapor deposition (CVD), physical vapor deposition
(PVD), or the like.
[0016] In the present embodiment, the DLC layer slides with respect
to the counter element on the surface in the opposite side of the
Cu-based bearing alloy layer, Hereinafter, the surface of the DLC
layer in the opposite side of the Cu-based bearing alloy layer that
slides with respect to the counter element is referred to as "the
slide surface of the DLC layer".
[0017] The shape of the sliding surface of the DLC layer is
controlled by controlling the speed of the DLC layer formation or
controlling the distribution of the hard particles residing on the
DLC layer side surface of the Cu-based bearing alloy layer.
[0018] The DLC layer grows in the direction of its thickness from
the hard particles exposed on the DLC layer side surface of the
Cu-based bearing alloy layer. Thus, the DLC layer grown from the
hard, particles exposed on the DLC layer side surface of the
Cu-based. bearing alloy layer reflects the planar shape of the
exposed hard particles. That is, portions of the slide layer of the
DLC layer that correspond to the hard particles exposed from, the
Cu-based bearing alloy layer results in a protrusion which is
protrusive as compared to other portions. Carbon constituting the
DLC layer forms a stronger bond with the hard particles comprising
group of elements similar to carbon such as borides, silicides,
oxides, nitrides, carbides, and intermetallic compounds, as
compared to Cu which is the primary component of the Cu-based
bearing alloy layer. Carbon constituting the DLC layer especially
exhibits high bonding force with hard particles comprising carbides
and silicides that include congeners such as carbon and silicon.
Thus, the hard, particles exposed from the Cu-based bearing alloy
layer serves as a medium to establish a stronger bond between the
DLC layer and the Cu-based bearing alloy layer. Further, the amount
of protrusion observed on the slide surface of the DLC layer
increases with the increase in the amount of protrusion of the hard
particles protruding toward the DLC layer side from the Cu-based
bearing alloy layer.
[0019] The protrusions formed on the slide surface of the DLC
layer, so as to correspond to the planar shapes of the hard
particles, are prone to receive load from the counter element.
Thus, frictional heat easily develops on the protrusions when the
protrusions formed on the slide surface of the DLC layer is in
sliding contact with the counter element. The frictional heat
facilitates graphitization of the protrusions formed on the slide
surface of the DLC layer and thus, the softening of the
protrusions, thereby reducing the resistance to shearing force.
Hence, shearing force applied to the DLC layer, when sliding with
the counter element, renders the DLC layer slippery which means
that the frictional coefficient of the DLC layer is reduced.
[0020] The protrusions reflecting the planar shapes of the hard
particles are formed on the slide surface of the DLC layer when the
DLC layer is formed at a certain speed which is hereinafter
referred to as a first, formation speed.
[0021] The slide surface of the DLC layer can be shaped relatively
flat, by controlling the formation speed of the DLC layer or
controlling the distribution of the hard particles exposed from the
Cu-based bearing alloy layer. The slide surface of the DLC layer,
when formed relatively flat, allows the load of the counter element
to be distributed throughout the slide surface of the DLC layer.
The DLC layer and the hard particles are harder than Al that serves
as the matrix of the Cu-based bearing alloy layer. Therefore, the
DLC layer formed on the hard particles exposed from the Cu-based
bearing alloy layer do not easily deform when load is applied to
the slide surface of the DLC layer.
[0022] In contrast, the DLC layer which is formed on Cu serving as
the matrix of the Cu-based bearing alloy layer where the hard
particles are not exposed, deforms easily toward the Cu-based
bearing alloy layer with the deformation of Cu when load is applied
from the sliding surface side of the DLC layer.
[0023] As a result, the load applied by the counter element is
prone to concentrate on the DLC layer located on the exposed hard
particles even when the load is evenly distributed throughout the
sliding surface of the flat DLC layer. Further, because the DLC
layer formed, on the hard particles exposed from the Cu-based
bearing alloy layer and the counter element are prone to come in
sliding contact, frictional heat readily develops at the contact
site. The frictional heat facilitates graphitization and thus, the
softening of the DLC layer formed, on the hard, particles, thereby
reducing the resistance to shearing force. Hence, shearing force
applied, to the DLC layer, when sliding with the counter element,
renders the DLC layer slippery, which means that the frictional
coefficient of the DLC layer is reduced.
[0024] The slide surface of the DLC layer becomes relatively flat
when the DLC layer is formed at a certain speed which is
hereinafter referred to as a second formation speed.
[0025] Further, as shown in FIG. 5, the DLC layer formed on the
hard particles exposed from the Cu-based bearing alloy layer can be
made thinner than the DLC layer formed at the second formation
speed by controlling the formation speed of the DLC layer or
controlling the distribution of the hard particles exposed from the
Cu-based bearing alloy layer. As a result, the DLC layer formed on
the hard particles exposed from the Cu-based bearing alloy layer
can be made thinner than other portions of the DLC layer. This
results in formation of recesses in the portions of the slide
surface of the DLC layer corresponding to the exposed hard
particles. Lubricating oil for lubricating the slide portion fills
the recess thus formed. This facilitates the lubrication between
the slide member and the counter element and renders the slide
member less friction prone. As a result, the requirement for
improvement in seizure resistance can also be achieved.
[0026] The slide surface of the DLC layer can be recessed by
forming the DLC layer at a certain speed referred to as a third
formation speed.
[0027] In the slide member of one embodiment of the present
invention, the hard particles exposed on the DLC layer side surface
are spaced from one another by an average distance ranging from 3
to 50 (.mu.m).
[0028] Arranging the average distance between the exposed hard,
particles to 50 (.mu.m) or less suppresses sparse distribution of
the hard particles exposed on the DLC layer side surface of the
Cu-based bearing alloy layer. Thus, it becomes easier for the
Cu-based bearing alloy layer and the DLC layer to exert high
bonding force therebetween. This results in improved seizure
resistance. Arranging the average distance between the exposed hard
particles to 3 (.mu.m) or greater, renders the count of protrusions
formed on the slide surface of the DLC layer and the size of the
recesses formed on the slide surface more suitable in terms of oil
film formation. This suppresses oil film ruptures and provides
outstanding seizure resistance. Controlling the average distance
between the hard particles secures the bonding force between the
Cu-based bearing alloy layer and the DLC layer of the Cu-based
bearing alloy layer as well as the seizure resistance. The average
distance preferably ranges from 5 to 45 (.mu.m).
[0029] In the slide member of one embodiment of the present
invention, the area percentage of the hard, particles exposed on
the DLC layer side surface with respect to a total area of the DLC
layer side surface ranges from 0.1 to 14 (%).
[0030] The total area of hard particles corresponds to the
projection area of hard, particles exposed on the DLC layer side
surface of the Cu-based bearing alloy layer, in other words, the
sum of the area which is occupied by the planar shape of the hard
particles. Thus, the area percentage is the percentage the total
area of the exposed hard particles occupies within the total area
of the DLC layer side surface of the Cu-based bearing alloy layer.
Further, the area percentage of the hard particles mentioned in
this specification indicates the sum of the projection area of
every hard particle residing on the unit area of the DLC layer side
surface of the Cu-based bearing alloy layer.
When the area percentage of the hard particles is 0.1 (%) or
greater, the hard particles increases their contribution to the
formation of the DLC layer. Thus, it becomes easier to form
protrusions and recesses on the slide surface of the DLC layer
through control of the formation speed of the DLC layer. Further,
when the area percentage is 0.1 (%) or greater, the area of contact
between the DLC layer and the hard particles is secured reliably to
allow relatively greater bonding force to be exerted between the
Cu-based bearing alloy layer and the DLC layer. By controlling the
area percentage as described above, delamination of the DLC layer
is suppressed more reliably to thereby improve the seizure
resistance. As opposed to this, when the area percentage is 14 (%)
or less, it becomes easier to prevent oversizing of protrusions and
recesses in the slide layer of the DLC layer regardless of the
formation speed of the DLC layer. Thus, arranging the area
percentage to 14 (%) or less is advantageous in terms of oil film
formation. It is further preferable to arrange the area percentage
to 14 (%) or less in terms of wear resistance. Due to the above
described reasons, the wear resistance and the seizure resistance
can be improved by controlling the area percentage. The preferable
range of the area percentage is 2 to 10%.
[0031] The total area of the hard particles exposed on the DLC
layer side surface of the Cu-based bearing alloy layer can be
controlled by modifying the particle diameter of the hard
particles.
[0032] The analysis on the area percentage of the hard particles is
done by capturing images of the DLC layer side surface of the
Cu-based bearing alloy layer with a microscope and putting the
captured images through an image analysis equipment. In doing so,
every hard particle residing within the observation field of, for
instance, 0.0125 mm.sup.2 is extracted and the area is calculated
for each of the extracted hard particles. The area percentage is
calculated based on the ratio of the area of the observation field
to the sum of the area of the hard particles. The area percentage
that the total area of the hard particles residing within the
observation field occupies within the area of the observation field
is equal to the area percentage that the total area of the hard
particles exposed on the DLC layer side surface of the Cu-based
bearing alloy layer occupies within the area of the DLC layer side
surface of the Cu-based bearing alloy layer. The area percentage
may be configured to vary in certain locations depending upon
usage.
[0033] In obtaining the particle diameter of the hard particles
exposed on the DLC layer side surface of the Cu-based bearing alloy
layer, the area of each hard particle residing within the 0.0125
mm.sup.2 observation field is measured. Then, an imaginary circle
is drawn which has an area identical to the measured area of the
hard particle and the diameter of the imaginary circle is converted
into the particle diameter.
[0034] In the slide member of one embodiment of the present
invention, A.gtoreq.0.5.times.T, where A (%) represents the area
percentage of the hard particles exposed on the DLC layer side
surface and T (.mu.m) represents the thickness of the DLC
layer.
[0035] Area percentage A (%) of the hard particles and thickness T
(.mu.m) of the DLC layer affect the friction produced in the
sliding movement. More specifically, it becomes easier to cause
shear slips within the DLC layer when a DLC layer, having a certain
hard particle area percentage, becomes thinner or when the area
percentage of the hard particles becomes greater in a DLC layer
having a certain thickness, thereby facilitating the reduction of
the friction coefficient. Area percentage A (%) of the hard
particles exposed on the DLC layer side surface and thickness T
(.mu.m) of the DLC layer are interrelated in the above described
manner.
[0036] In the slide member of one embodiment of the present
invention, H.ltoreq.10000/T, where H(HV) represents the hardness of
the DLC layer and T (.mu.m) represents the thickness of the DLC
layer.
[0037] The influence of the hard particles in causing the above
described difference in the hardness of the DLC layer becomes
greater when H.ltoreq.10000/T, where H (HV) represents the hardness
of the DLC layer and T (.mu.m) represents the thickness of the DLC
layer. When the hardness relative to the thickness of the DLC layer
is controlled within the above range, it becomes easier to
effectively facilitate the graphitization of the exceptionally wear
resistant slide surface of the DLC layer based on the
presence/absence of the hard, particles. The controlled correlation
between the hardness and the thickness of the DLC layer achieves
both reduction in friction coefficient and improvement in wear
resistance.
[0038] In the slide member of one embodiment of the present
invention, the DLC layer satisfies H.ltoreq.6000, and T.ltoreq.15.
This means that hardness H of the DLC layer is H.ltoreq.6000 (HV)
and thickness T of the DLC layer is T.ltoreq.15 (.mu.m).
[0039] When the thickness of the DLC layer is equal to or less than
15 (.mu.m), it becomes easier to form, on the slide surface of the
DLC layer, convexes and concaves that reflect the hard particles
exposed from the Cu-based bearing alloy layer. The above described
thickness of the DLC layer is obtained by controlling the duration
of methodologies such as plasma enhanced CVD and PVD employed in
forming the DLC layer.
[0040] Further, when hardness H of the DLC layer is equal to or
less than 6000 (HV), the aggression of the DLC layer on the counter
element can be readily suppressed while achieving sufficient wear
resistance. The hardness of the DLC layer may be modified through
adjustments in the content of additive elements such as hydrogen,
Si, Ti, and W in the DLC layer and the ratio of hybrid orbital
(sp.sup.2/sp.sup.3) in the DLC layer.
[0041] In the slide member of one embodiment of the present
invention, the hardness of the DLC layer is 1.1 times or greater
the hardness of the Cu-based bearing alloy layer and 0.9 times or
less the hardness of the counter element with which the DLC layer
slides.
[0042] When the hardness of the DLC layer is 1.1 times or greater
the hardness of the Cu-based bearing alloy layer, the DLC layer
exerts its wear resistance more effectively. On the other hand,
when the hardness of the DLC layer is 0.9 times or less the
hardness of the counter element with which it slides, the wear of
the counter element can be suppressed more reliably. Thus,
specifying the hardness of the DLC layer in the above described
manner reduces the wear of both the DLC layer and the counter
element.
[0043] Between the Cu-based bearing alloy layer and the DLC layer,
an intermediate layer may be provided to improve the bonding
between them. The intermediate layer preferably comprises metal
such as Si, Ti, Cr, and W or carbides and nitrides. The
intermediate layer may vary its composition in the thickness
direction. For instance, When the intermediate layer is a Si--C
system or a Ti--C system, the concentration of Si or Ti may be
arranged to be relatively higher in the Cu-based bearing alloy
layer side, whereas the concentration of C may be arranged to be
relatively higher in the DLC layer side.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] [FIG. 1] A cross sectional view schematically indicating a
slide member of one embodiment of the present invention.
[0045] [FIG. 2] A transverse plan view schematically indicating a
slide surface of an Cu-based bearing alloy layer of a slide member
of one embodiment.
[0046] [FIG. 3] A cross sectional view schematically indicating a
slide member in which a DLC layer is formed at a first formation
speed.
[0047] [FIG. 4] A cross sectional view schematically indicating a
slide member in which the DLC layer is formed at a second formation
speed.
[0048] [FIG. 5] A cross sectional view schematically indicating a
slide member in which the DLC layer is formed at a third formation
speed.
[0049] [FIG. 6A and 6B] A chart specifying EXAMPLES and COMPARATIVE
EXAMPLES of a slide member of one embodiment.
[0050] [FIG. 7] A chart indicating the relation between the
hardness and the thickness of the DLC layer.
EMBODIMENTS OF THE INVENTION
[0051] The slide member of the present embodiment is illustrated in
FIG. 1. Slide member 1 shown in FIG. 1 is provided with Cu-based
bearing alloy layer 2 and DLC layer 3. Cu-based bearing alloy layer
2 is provided over a metal backing not shown. DLC layer 3 is
provided over Cu-based bearing alloy layer 2. As shown in FIG. 2,
Cu-based bearing alloy layer 2 comprises Cu matrix 2a and hard
particles 2b. In other words, Cu-based bearing alloy layer 2
contains hard particles 2b within Cu matrix 2a. Hard particles 2b
contained in Cu-based bearing alloy layer 2 are at least partially
exposed on DLC layer 3 side surface of Cu-based bearing alloy layer
2. Being "exposed" in this context indicates either the state in
which hard particles 2b are located on a plane coincidental with
DLC layer 3 side surface of Cu-based bearing alloy layer 2 or the
state in which hard particles 2b protrude toward DLC layer 3 from
the surface.
[0052] When DLC layer 3 is formed at the first formation speed, DLC
layer 3 is shaped as shown in FIG. 3. That is, the slide surface of
DLC layer 3 forms protrusions 4 reflecting the shapes of hard,
particles 2b exposed on DLC layer 3 side surface of Cu-based
bearing alloy layer 2.
[0053] When DLC layer 3 is formed at the second formation speed,
DLC layer 3 is shaped as shown in FIG. 4. That is, the slide
surface of DLC layer 3 forms planar surface 3a regardless of the
shapes of hard particles 2b exposed, on DLC layer 3 side surface of
Cu-based. bearing alloy layer 2.
[0054] When DLC layer 3 is formed at the third formation speed, DLC
layer 3 is shaped, as shown in FIG. 5. That is, the slide surface
of DLC layer 3 forms recesses 5 reflecting the shapes of hard
particles 2b exposed on the DLC layer 3 side surface of Cu-based
bearing alloy layer 2.
[0055] Next, a description is given on a method of manufacturing a
slide member of the present embodiment.
[0056] First, Cu powder is mixed with hard particles having the
particle diameter being prearranged to a predetermined size and
with other powder components at a predetermined mass percentage. In
the present embodiment, hard particles comprise Mo.sub.2C. The Cu
powder may be replaced by Cu alloy powder comprising Cu--Sn--Ni
alloy and Cu--Sn--Ni--Zn alloy. Further, 2 or more types of hard
particles may be mixed.
[0057] Next, the power mixture of Cu powder and hard particles is
dispersed on a strip of steel sheet which is 1.3 mm thick. The
strip of steel sheet corresponds to a metal backing and has a Cu
plating provided on it in advance. Next, the powder-dispersed steel
sheet is heated for approximately 15 minutes in a reducing
atmosphere of 800 to 950.degree. C. The powder-dispersed steel
sheet is subjected to initial sintering to form a Cu-based bearing
alloy layer with the Cu powder and hard particles. Then, the steel
sheet having the Cu-based bearing alloy layer formed on it is
repeatedly rolled, and sintered for densification. This forms the
steel sheet having the Cu-based bearing alloy layer formed on it
into a bimetal which is approximately 1.6 mm thick and in which the
Cu-based bearing alloy layer is approximately 0.4 mm thick. The
obtained bimetal was formed into a semi cylindrical shape.
[0058] The bimetal formed into a semi cylindrical shape further
forms a DLC layer thereon by treating its inner peripheral surface
with an ordinary plasma enhanced CVD or PVD.
[0059] Samples of a slide member were fabricated in the above
described manner and verified for their friction coefficient.
[0060] More specifically, EXAMPLES obtained by the manufacturing
method of the present embodiment may form the DLC layer at various
controlled speeds. When the DLC layer is formed at the first
formation speed, protrusions can be formed on the sliding surfaces
of the DLC layer. When the DLC layer is formed at the second
formation speed, a relatively flat slide surface can be obtained.
When the DLC layer is formed at the third formation speed, recesses
can be formed on the sliding surface of the DLC layer. Among
EXAMPLES indicated in FIG. 6, EXAMPLE 1 forms the DLC layer at the
first formation speed as shown in FIG. 3. EXAMPLE 2 forms the DLC
layer at the second formation speed as shewn in FIG. 4. EXAMPLE 3
forms the DLC layer at the third formation speed as shown in FIG.
5. Further, EXAMPLES 4 to 24 and COMPARATIVE EXAMPLE 1 each forms
the DLC layer at the second formation speed. COMPARATIVE EXAMPLE 1
used for comparison in the verification does not. contain Si in the
Cu-based bearing alloy layer. COMPARATIVE EXAMPLE 2 is not
provided, with a DLC layer. Description will be given hereinafter
on EXAMPLES and COMPARATIVE EXAMPLES based on FIG. 6.
[0061] (Regarding Cu-Based Bearing Alloy Layer)
[0062] The Cu-based bearing alloy layer of EXAMPLES 1 to 24, and
COMPARATIVE EXAMPLE 1 and 2 are each formed of Cu-based Cu alloy
including 6 mass (%) of Sn, 3 mass (%) of Ni, and 5 mass(%) of
Bi.
[0063] (Regarding Component of Hard Particles)
[0064] In EXAMPLES 1 to 3 and COMPARATIVE EXAMPLE 2, the hard
particles comprise Al.sub.2O.sub.3. In EXAMPLES 4, 6, 7, and 10 to
24, the hard particles comprise Mo.sub.2C. In EXAMPLES 5, 8, and 9,
the hard particles comprise TiSi.sub.2. Stated differently, with
the exception of EXAMPLES 1 to 3 and COMPARATIVE EXAMPLE 2, the
hard particles of EXAMPLES comprise silicides of metal or carbides
of metal.
[0065] (Regarding Average Particle Diameter of Hard Particles)
[0066] In EXAMPLES 1 to 8, 10 to 24, and COMPARATIVE EXAMPLE 2, the
average particle diameter of the hard particles exposed on the DLC
layer side of the Cu-based bearing alloy layer ranges from 0.5 to
20 (.mu.m). In EXAMPLE 9, the average particle diameter of the hard
particles is configured to 25 (.mu.m).
[0067] (Regarding Average Distance Between Hard Particles)
[0068] In EXAMPLES 1 to 6, 8, 10 to 12, and 14 to 24, the average
distance between the hard particles exposed on the DLC layer side
surface of the Cu-based bearing alloy layer ranges from 3 to 50
(.mu.m). As opposed to this, in EXAMPLE 7, the average distance
between the hard, particles is configured to 80 (.mu.m); in EXAMPLE
9, the average distance between the hard, particles is configured
to 90 (.mu.m); and in EXAMPLE 13, the average distance between the
hard particles is configured to 55 (.mu.m).
[0069] (Regarding Area Percentage of Hard Particles)
[0070] In EXAMPLES 1 to 6, 8, 10, 12, 14, 15, and 17 to 24, the
area percentage of the hard, particles ranges from 0.1 to 14(%). As
opposed to this, in EXAMPLE 7, the area percentage of the hard,
particles is configured to 0.08 (%); in EXAMPLE 9, the area
percentage of the hard particles is configured to 0.07 (%); in
EXAMPLES 11 and 13, the area percentage of the hard particles is
configured to 0.09 (%); and in EXAMPLE 16, the area percentage of
the hard particles is configured to 0,05 (%). The area percentage
of the hard particles in the foregoing EXAMPLES is less than 0.1
(%).
[0071] (Regarding Relation Between Hardness and Thickness of DLC
Layer)
[0072] In EXAMPLES 1 to 24, the relation between hardness (H) and
thickness (T) of DLC all satisfy H.ltoreq.10000/T. Hardness H and
thickness T of the DLC layer relate to one another as shown in FIG.
7. EXAMPLES 1 to 24 are plotted in the shaded region located closer
to the origin from the curve derived from H.ltoreq.10000/T.
[0073] (Relation Between Area Percentage of Hard Particles And
thickness of DLC Layer)
[0074] In EXAMPLES 1 to 6, 8, 10, 12, 15, and 17 to 24, area
percentage A (%) of the hard particles exposed on the DLC layer
side surface of the Cu-based bearing alloy layer and thickness T of
the DLC layer satisfy A.gtoreq.0.5.times.T. In contrast,
A.ltoreq.0.5.times.T in EXAMPLES 7, 9, 11, 13, 14, and 16.
[0075] (Regarding Adhesion Test)
[0076] EXAMPLES 1 to 24 and COMPARATIVE EXAMPLE 1 in FIG. 6 were
tested for the adhesion of the Cu-based bearing alloy layer and the
DLC layer. The adhesion of the DLC layer was tested by peeling the
DLC layer through application of delamination load. More
specifically, the DLC layer is subjected to continuous delamination
load ranging from 0 (N) to 300 (N). The distance of movement during
the application of the delamination load is configured to 10 (mm).
The lamination load is given by a spherical element and is made of
chrome steel (SUJ-2) which is 3 (mm) in diameter. Further, when
applying the delamination load, 10 (.mu. liters) of lubricant was
supplied between the slide member and the spherical element.
[0077] The delamination load in which delamination was observed in
the DLC layer of each sample is as indicated in FIG. 6. The results
snow that the delamination load in EXAMPLES 1 to 24 were equal to
or greater than 110 (N). In contrast, COMPARATIVE EXAMPLE 1 exhibit
a delamination load of 100 (N). It can be understood from above
that in EXAMPLES 1 to 24 of the present embodiment in which the
hard particles are exposed on the DLC layer side surface of the
Cu-based bearing alloy layer, the DLC layer is highly adhesive
compared to COMPARATIVE EXAMPLES 1 and 2 that do not contain hard
particles. In other words, it is clear that the hard particles
exposed on the DLC layer side surface of the Cu-based bearing alloy
layer is a contributing factor in improving the bonding between the
DLC layer and the Cu-based bearing alloy layer.
[0078] With reference to EXAMPLES 2, 4, and 5, verification is made
on how the components of the hard particles affect the delamination
load. Referring to FIG. 6, EXAMPLE 4 in which hard particles
comprises Mo.sub.2C which is a metal carbide and EXAMPLE 5 in which
hard particles comprise TiSi.sub.2 which is a metal silicide show
improved delamination load as compared to EXAMPLE 1 in which hard,
particles comprise Al.sub.2O.sub.3 which is a metal oxide. This is
an indication that, hard particles, when made of a metal carbide or
a metal, silicide, increases its contribution to the bonding of the
Cu-based bearing alloy layer and the DLC layer.
[0079] The above described results indicate that the delamination
load, in other words, the contribution of the hard particles to the
bonding of the Cu-based bearing alloy layer and the DLC layer is
increased when the average particle diameter of the hard particles
is 20 (.mu.m) or less. For example, in comparison with EXAMPLE 9 in
which the average particle diameter of the hard particles exceeds
20 (.mu.m), the delaimination load is improved in other EXAMPLES
having approximating conditions. This is an indication that the
average particle diameter of the hard particles exposed on the DLC
layer side surface of Cu-based bearing alloy layer is preferably 20
(.mu.m) or less.
[0080] The above described results further indicate that the
contribution of the hard particles to the bonding of the Cu-based
bearing alloy layer and the DLC layer is increased when the average
distance between the hard particles is 50 (.mu.m) or less. For
example, in comparison with EXAMPLES 7, 9, and 13 in which the
average distance between the hard particles exceeds 50 (.mu.m), the
delaimination load is improved in other EXAMPLES having
approximating conditions. This is an indication that the average
distance between the hard particles exposed on the DLC layer side
surface of the Cu-based bearing alloy layer is preferably 50
(.mu.m) or less.
[0081] The above described results further indicate that the
contribution of the hard particles to the bonding of the Cu-based
bearing alloy layer and the DLC layer is increased when the area
percentage A of the hard particles is 0.1 (%) or greater. For
example, in comparison with EXAMPLES 7, 9, 11, 13, and 16 in which
the area percentage of the hard particles is less than 0.1 (%) ,
the delamination load is improved in other EXAMPLES having
approximating conditions, This is an indication that the area
percentage of the hard particles exposed on the DLC layer side
surface of Cu-based bearing alloy layer is preferably 0.1 (%) or
greater.
(Regarding Seizure Test)
[0082] EXAMPLES 1 to 24 and COMPARATIVE EXAMPLES 1 and 2 were
tested for their seizure resistance. Based on the standpoint that
seizure resistance can be improved by reducing friction, reduction
of friction coefficient was verified. Seizure resistance was
tested, under the following conditions. The samples being tested
were spun at the speed of 2 (m/sec) relative to the counter shaft
and subjected, to a test load of 1 (MPa/5 min). The lubricating oil
applied to the samples was SAE#30 which was supplied in the amount
of 20 (ml/min) at the temperature of 60 (.degree.C). The counter
shaft was made of carbon steel (S55C) which possessed a hardness of
600 (HV). Further, in EXAMPLE 23, a counter shaft comprising a
quenched carbon steel (S55C) was used whereas, in EXAMPLES 21 and
24, a counter shaft comprising a carbon steel (S55C) with a DLC
coating was used.
[0083] The specific load (MPa) in which seizure was observed in the
samples is indicated in FIG. 6. Seizure was deemed to have
occurred. in the samples when the temperature of the surface on the
backside, that is, the opposite side of the slide surface exceeded
250 (.degree.C), or when the frictional force produced between the
sample and the counter shaft exceeded 50 (N). According to FIG. 6,
the specific load in which seizure was observed in EXAMPLES 1 to 24
was equal to or greater than 19 (MPa). In contrast, the specific
load in which seizure was observed in COMPARATIVE EXAMPLES 1 and 2
was equal to or less than 11 (MPa). This is an indication that
EXAMPLES 1 to 24, in which the DLC layer was formed above the DLC
layer side surface of the Cu-based bearing alloy layer on which the
hard particles were exposed, showed relatively greater seizuring
specific load, in other words, higher seizure resistance, which in
turn is an indication of relatively small friction coefficient. In
particular, in EXAMPLES 1 to 6, 8, 10, 12, 15, and 17 to 24,
thickness T and area percentage A of the DLC layer were controlled
to a specific range. Thus, improved seizure resistance was observed
in EXAMPLES 1 to 6, 8, 10, 12, 15, and 17 to 24 as compared to
EXAMPLES formed in approximating conditions.
[0084] In EXAMPLES 1 to 20, 22, and COMPARATIVE EXAMPLES 1 and 2
shown in FIG. 6, the counter shaft, sliding with the samples were
made of carbon steel (S55C) having a slide portion exhibiting a
hardness of 600 (HV). As opposed to this, in EXAMPLES 21 and 24,
the counter shaft had a DLC layer coated over the slide surface of
the carbon steel (S55C). In EXAMPLE 21, the hardness of the slide
portion of the counter shaft measured 5000 (HV). In EXAMPLE 24, the
hardness of the slide portion of the counter shaft measured 2000
(HV). Further in EXAMPLE 23, the counter shaft comprises quenched
carbon steel (S55C) and the hardness of the slide portion measured
700 (HV). Further, in EXAMPLE 20, the hardness of the slide portion
of the counter shaft measured 600 (HV) while the hardness of the
DLC layer measured 500 (HV). In EXAMPLE 22, the hardness of the
slide portion of the counter shaft measured 600 (HV) while the
hardness of the DLC layer measured 110 (HV). EXAMPLES 20 to 24 in
which the hardness of the DLC layer was configured to be 0.9 times
or less the hardness of the slide portion of the counter shaft
showed improvement in seizuring specific load. In other words,
EXAMPLES 20 to 24 in which the hardness of the DLC layer was
configured to be 0.9 times or less the hardness of the slide
portion of the counter shaft produced less abrasion powder as
compared to EXAMPLES that do not meet this hardness condition and
showed improved seizuring specific load.
[0085] (Effect of Formation Speed of DLC Layer)
[0086] EXAMPLES 1, 2, and 3 indicated in FIG. 6 form the DLC layer
at different speeds. More specifically, EXAMPLE 1 forms the DLC
layer shown in FIG. 3 at the first formation speed, EXAMPLE 2 forms
the DLC layer shown in FIG. 4 at the second formation speed, and
EXAMPLE 3 forms the DLC layer shown in FIG. 5 at the third
formation speed. Further, EXAMPLES 1 to 3 have identical properties
such as the Cu alloy component, hard particle component, average
particle diameter of hard particles, and average distance between
the hard particles. However, EXAMPLES 1 to 3 do not differ
significantly in delamination load, and seizuring specific load.
This is an indication that influence of the formation speed of the
DLC layer on delamination load and seizuring specific load is
small. Because the influence of the formation speed of the DLC
layer on the properties of the slide member is small, EXAMPLES 4 to
22 and COMPARATIVE EXAMPLE 1 form the DLC layer at the second
formation speed.
[0087] By forming a DLC layer on the Cu-based bearing alloy layer,
EXAMPLES 1 to 24 described above allow reduction in the friction
when sliding with the counter shaft. EXAMPLES 1 to 24 showed
relatively higher bonding force between the Cu-based bearing alloy
layer and the DLC layer as compared to COMPARATIVE EXAMPLES 1 and
2, thereby improving the seizure resistance and reducing friction
at the same time.
[0088] The present embodiment may be implemented after
modifications within the scope of its spirit. Though not described,
each of the components may include inevitable impurities.
* * * * *